title: Reducing metallic artifacts in postoperative spinal imaging: usefulness of IDEAL contrast-enhanced T1- and T2-weighted MR imaging--phantom and clinical studies.
abstract: OBJECTIVE
  To prospectively compare the effectiveness of iterative decomposition of water and fat with echo asymmetry and least-squares estimation (IDEAL) T2-weighted and contrast material-enhanced T1-weighted magnetic resonance (MR) imaging with that of a conventional MR imaging protocol in minimizing metallic artifacts in phantoms and in patients with metallic hardware after spinal surgery.
  
  
  METHODS
  Institutional review board approval and informed consent were obtained for this study. Coronal T1- and T2-weighted MR images of six titanium alloy pedicle screws in an oil bath containing tubes filled with diluted gadolinium contrast medium were obtained with frequency-selective fat saturation (FSFS) and IDEAL. Axial T2-weighted and contrast-enhanced T1-weighted MR imaging of the spine was performed with FSFS and IDEAL at 22 lumbar levels in 19 patients. Two musculoskeletal radiologists qualitatively analyzed the images in terms of the visualization of paravertebral muscle and the spinal canal region, uniformity of fat saturation, and noise. The paired images were rated by using a five-point scale. For the quantitative study with phantoms, the short- and long-axis lengths of metallic artifacts were determined on signal intensity profiles.
  
  
  RESULTS
  In the phantom study, metallic artifact size was markedly decreased in the IDEAL T2-weighted and contrast-enhanced T1-weighted images (P < .001). In the clinical study, IDEAL T2-weighted and contrast-enhanced T1-weighted images enabled significantly improved visualization of the dural sac (P < .001), spinal muscles (P < .05), uniformity of fat saturation (P < .001), and noise (P < .05).
  
  
  CONCLUSIONS
  IDEAL T2-weighted and contrast-enhanced T1-weighted MR imaging examinations effectively reduce the degree of tissue-obscuring artifacts produced by spinal fixation hardware and improve image quality compared with FSFS T2-weighted and contrast-enhanced T1-weighted MR imaging.
  
  
  BACKGROUND
  http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.11101856/-/DC1.
authors.affiliation: Department of Radiology, Soonchunhyang University Hospital, 1174 Jung-Dong, Wonmi-Gu, Bucheon-Si, Gyeonggi-Do 420-767 Korea. mj4907@schmc.ac.kr
authors.forename: Jang Gyu
authors.initials: JG
authors.lastname: Cha
authors.forename: Wook
authors.initials: W
authors.lastname: Jin
authors.forename: Min Hee
authors.initials: MH
authors.lastname: Lee
authors.forename: Dong Hoon
authors.initials: DH
authors.lastname: Kim
authors.forename: Jai Soung
authors.initials: JS
authors.lastname: Park
authors.forename: Won Han
authors.initials: WH
authors.lastname: Shin
authors.forename: Boem Ha
authors.initials: BH
authors.lastname: Yi
mesh_terms: D000328:Adult; D000368:Aged; D016477:Artifacts; D003287:Contrast Media; D005260:Female; D005682:Gadolinium; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D016268:Internal Fixators; D016018:Least-Squares Analysis; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D019047:Phantoms, Imaging; D011446:Prospective Studies; D013131:Spine / Q000601:surgery*; D014025:Titanium
chemical_list: D003287:Contrast Media; D005682:Gadolinium; D014025:Titanium